As is well-known, a conductive layer is often formed on a substrate in manufacturing various electronic parts, e.g., thin film magnetic heads or very-large-scale integration (VLSI) chips, to electrically connect components located on the substrate. As the number of components on the substrate increases, a single conductive layer cannot accommodate all the components therein, and it becomes necessary to use a number of multiple conductive layers stacked on top of another, with a layer of insulating material between two successive conductive layers.
However, each conductive layer has a non-negligible finite thickness and in forming the stack of conductive layers, the thickness usually causes forming protuberances on the insulating layer placed on top of the respective conductive layer, the protuberances making it progressively difficult to stack the conductive layers on top of another. Further, there are additional difficulties associated with this method, one of them being that, in order to obtain the protuberances with sides that are not too steep, the respective conductive layer must first be patterned in such a way that sides thereof are not too steep, and this involves a number of difficult processing steps.